PMID:12356333

Citation	Lloyd, JR, Leang, C, Hodges Myerson, AL, Coppi, MV, Cuifo, S, Methe, B, Sandler, SJ and Lovley, DR (2003) Biochemical and genetic characterization of PpcA, a periplasmic c-type cytochrome in Geobacter sulfurreducens. Biochem. J. 369:153-61
Abstract	A 9.6 kDa periplasmic c -type cytochrome, designated PpcA, was purified from the Fe(III)-reducing bacterium Geobacter sulfurreducens and characterized. The purified protein is basic (pI 9.5), contains three haems and has an N-terminal amino acid sequence closely related to those of the previously described trihaem c (7) cytochromes of Geobacter metallireducens and Desulfuromonas acetoxidans. The gene encoding PpcA was identified from the G. sulfurreducens genome using the N-terminal sequence, and encodes a protein of 71 amino acids (molecular mass 9.58 kDa) with 49% identity to the c (7) cytochrome of D. acetoxidans. In order to determine the physiological role of PpcA, a knockout mutant was prepared with a single-step recombination method. Acetate-dependent Fe(III) reduction was significantly inhibited in both growing cultures and cell suspensions of the mutant. When ppcA was expressed in trans, the full capacity for Fe(III) reduction with acetate was restored. The transfer of electrons from acetate to anthraquinone 2,6-disulphonate (AQDS; a humic acid analogue) and to U(VI) was also compromised in the mutant, but acetate-dependent reduction of fumarate was not altered. The rates of reduction of Fe(III), AQDS, U(VI) and fumarate were also the same in the wild type and ppcA mutant when hydrogen was supplied as the electron donor. When taken together with previous studies on other electron transport proteins in G. sulfurreducens, these results suggest that PpcA serves as an intermediary electron carrier from acetate to terminal Fe(III) reductases in the outer membrane, and is also involved in the transfer of electrons from acetate to U(VI) and humics.
Links	PubMed PMC1223068 Online version:10.1042/BJ20020597
Keywords	Amino Acid Sequence; Base Sequence; Cytochrome c Group/genetics; Cytochrome c Group/metabolism; DNA, Bacterial; Molecular Sequence Data; Periplasm/enzymology; Proteobacteria/enzymology; Sequence Homology, Amino Acid
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
GEOSN:Q8GGK7		GO:0009055: electron carrier activity	ECO:0000315:		F		Figure 5 show the growth rate of both wild type and ppcA mutants when grown with acetate as an electron donor and both fumarate and iron(III) as electron acceptors. The growth rate of the mutant was decreased when Fe(III) was used as an electron acceptor. Combined with Table 3 which illustrates the reduction rates of several compounds in wild type an mutant suggests that ppcA is a carrier of electrons from acetate to iron(III) reductases.	complete CACAO 4284

References

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